Rotor assembly and method of forming

ABSTRACT

A rotor assembly for a supercharger is provided having a first rotor section and at least one other rotor section affixed to the first rotor section. The first rotor section and the at least one other rotor section are formed from powdered metal and are substantially similar in shape. Each of the first rotor section and the at least one other rotor section has a plurality of lobes that are substantially hollow. The first rotor section and the at least one other rotor section are affixed through one of brazing, copper infiltration, and welding. A supercharger assembly incorporating the disclosed rotor assembly is also provided. Furthermore, a method of forming the disclosed rotor assembly is provided.

TECHNICAL FIELD

The present invention relates to rotor assemblies and a method of forming rotor assemblies for a compressor or supercharger.

BACKGROUND OF THE INVENTION

Roots-type or screw-type positive displacement compressors are employed in industrial and automotive applications. The compressor or supercharger may be operatively connected to an internal combustion engine to increase the amount or volume of intake air communicated to the internal combustion engine and thus provide for increased performance. The supercharger typically includes two interleaved counter-rotating rotors, each of which may be formed with a plurality of helical shaped lobes to convey volumes of intake air from an inlet passage to an outlet passage for subsequent introduction to the internal combustion engine.

Engine designers may include a selectively engageable clutch, such as an electrically operated clutch, disposed between an input pulley and the supercharger to selectively disengage the supercharger, i.e. stop or slow the rotation of the rotors contained therein, when its operation is not required, such as low engine load operation. As a result, the operating efficiency of the internal combustion engine may be increased. The durability and reliability of the clutch is largely a function of the inertia of the rotors which, in turn, is a function of the size and mass of the rotor lobes.

SUMMARY OF TIE INVENTION

A rotor assembly for a supercharger is provided having a first rotor section and at least one other rotor section affixed to the first rotor section. The first rotor section and the at least one other rotor section are formed from powdered metal and are substantially similar in shape. Each of the first rotor section and the at least one other rotor section has a plurality of lobes that are substantially hollow. The first rotor section and the at least one other rotor section are affixed through one of brazing, copper infiltration, and welding. Each of the first rotor section and the at least one other rotor section has at least one axially extending locating feature and at least one recess. The at least one recess of the first rotor section cooperates with the at least one axially extending locating feature of the at least one other rotor section to locate the first rotor section with respect to the at least one other rotor section. The rotor sections may be formed from one of steel, aluminum, and aluminum alloys. A supercharger assembly incorporating the disclosed rotor assembly is also provided.

A method of forming the rotor assembly described hereinabove is also provided. The method includes the steps of: A) forming a plurality of rotor sections from powdered metal; B) indexing adjacent rotor sections utilizing the locating features and recesses; and C) affixing the rotor sections with respect to each other to form the rotor assembly.

The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic perspective view of a supercharger configured for use with an internal combustion engine;

FIG. 2 is a perspective view of a rotor for use with the supercharger of FIG. 1;

FIG. 3 is a perspective view of a rotor section configured to form the rotor of FIG. 2;

FIG. 4 is another perspective view of the rotor section of FIG. 3; and

FIG. 5 is a perspective view of an alternate embodiment of a rotor for use with the supercharger of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings wherein like reference numbers correspond to like or similar components throughout the several figures, there is shown in FIG. 1 a compressor or supercharger assembly, generally indicated at 10. The supercharger 10 includes a housing 12. The housing 12 defines an inlet passage 14 configured to induct intake air, represented by arrow 16, into the supercharger assembly 10. The housing 12 further defines an outlet passage 18 configured to exhaust the intake air 16 from the supercharger assembly 10.

A rotor cavity 20 is defined by the housing 12 and is configured to contain a first and second rotor assembly 22 and 24, respectively, rotatably disposed therein. The first and second rotor assemblies 22 and 24 are interleaved and counter-rotating with respect to each other. The first rotor assembly 22 includes a plurality of lobes 26 extending radially outward in a clockwise twisting helical shape, as viewed from the inlet passage 14, while the second rotor assembly 24 includes a plurality of lobes 28 extending radially outward in a counterclockwise twisting helical shape, as viewed from the inlet passage 14. The first and second rotor assemblies 22 and 24 cooperate to convey volumes of intake air 16 from the inlet passage 14 to the outlet passage 18. The first and second rotor assemblies 22 and 24 are rotatably supported within the rotor cavity 20 by a respective first and second shaft member 30 and 32. The construction of the first and second rotor assemblies 22 and 24 is discussed in greater detail hereinbelow with reference to FIGS. 2 through 5. It should be understood that the construction of the second rotor assembly 24 is substantially similar to that of the first rotor assembly 22. For simplicity, the discussion hereinbelow will focus on the construction of the first rotor assembly 22, it being understood that the disclosed structure and method of forming are equally applicable to the second rotor assembly 24.

Referring to FIG. 2, there is shown a perspective view of the first rotor assembly 22 having lobes 26 extending generally radially outward from a hub portion 34 in a helical shape. Each of the lobes 26 define a cavity 36, such that the lobes 26 may be generally referred to as hollow. Advantageously, the cavities 36 of lobes 26 provide a reduction in rotational inertia over solid lobes, which may increase the reliability and durability of a selectively engageable clutch, not shown, configured to selectively deactivate the supercharger assembly 10 of FIG. 1. The first rotor assembly 22 is formed from a plurality of rotor sections 38. Each of the rotor sections 38 is preferably formed from sintered or powdered metal such as steel, aluminum and its alloys, etc. Each of the rotor sections 38 are preferably the same shape such that they may be formed from the same tooling. Additionally, by forming each of the rotor sections 38 with helical lobes 26, the resulting first rotor assembly 22 will have a near net shape once the rotor sections 38 are assembled thereby reducing the number of machining operations required to finish the first rotor assembly 22. The rotor sections 38 are affixed or attached to each other and mounted on the first shaft member 32 which extends through a bore 40, shown in FIGS. 3 and 4, defined by the hub portion 34 of the first rotor assembly 22.

Referring now to FIG. 3, there is shown a perspective view of an individual rotor section 38. The rotor section includes a first face 42 and a second face 44, shown in FIG. 4. The first face 42 includes locating features 46 extending generally axially therefrom. The locating features 46 are shown as being generally semi-spherical in shape; however, those skilled in the art will recognize other shapes may be provided, such as cylinders, pyramids, cubes, etc. while remaining within the scope of that which is claimed. As shown in FIG. 4, the second face 44 of the rotor section 38 defines recesses 48 sufficiently configured to receive locating features 46 of an adjacent rotor section, thereby indexing or providing a measure of alignment between adjacent rotor sections 38 of the first rotor assembly 22 of FIG. 2.

With reference to FIGS. 2 through 4, a method of forming the first rotor assembly 22 may be described. The method includes the steps of: A) forming the plurality of rotor sections 38 from powdered metal; B) indexing adjacent rotor sections 38 utilizing the locating features 46 and recesses 48; and C) affixing the rotor sections 38 with respect to each other to form the first rotor assembly 22. As mentioned hereinbefore the rotor sections 38 may be formed from steel or aluminum and its alloys. For rotor sections 38 formed from steel, adjacent rotor sections 38 may be affixed to one another through welding, brazing, or copper infiltration techniques. By copper infiltrating the rotor sections 38 to form the first rotor assembly 22, a measure of resistance against scuffing during operation of the super charger 10, shown in FIG. 1, may be provided. Alternately, for rotor sections 38 formed from aluminum and its alloys, adjacent rotor sections 38 may be affixed to one another through welding or brazing.

Referring now to FIG. 5 there is shown an alternate embodiment of the first rotor assembly 22 of FIGS. 1 through 4, generally indicated at 22A. The rotor assembly 22A includes a plurality of rotor sections 38A formed from sintered or powdered metal, such as steel or aluminum and its alloys. The rotor sections 38A have a plurality of lobes 26A extending generally radially outward from a hub portion 34A. The rotor sections 38A are similar to the rotor sections 38 of FIGS. 2 through 4, except that the rotor sections 38A are generally straight in the axial direction as opposed to the generally helical shape of rotor sections 38. As such, the rotor sections 38A must be affixed to each other in a slightly offset fashion to form the helical shape of the lobes 26A of the rotor assembly 22A thereby requiring a greater number of machining operations to finish the rotor assembly 22A when compared to that of the first rotor assembly 22. The bracketed portion, indicated at 50, illustrates the rotor assembly 22A prior to finish machining, while the bracketed portion, indicated at 52, illustrates the rotor assembly 22A after finish machining. The method of forming the rotor assembly 22A is substantially similar the method of forming the first rotor assembly 22 described hereinabove.

By forming the rotor assemblies 22 and 22A from powdered metal rotor sections 38 and 38A, respectively, flexibility in rotor length may be provided with no or minor changes in tooling. Additionally, by forming the rotor assemblies 22 and 22A from rotor sections 38 and 38A, the respective lobes 26 and 26A may be formed substantially hollow at reduced tooling complexity over traditional rotor forming techniques such as die-casting and investment casting. Furthermore, the amount of scrap rate may be substantially reduced over traditional rotor forming techniques. Those skilled in the art will recognize that the rotor assemblies 22 and 22A may be formed from a single rotor section 38 and 38A, formed form powdered metal, while remaining within the scope of that which is claimed. While the discussion hereinabove has focused on rotor assembly designs having a generally helical-type or screw-type form, those skilled in the art will recognize that the general principles may be applied to rotor assemblies having a generally straight form, such as those used in roots-type superchargers, while remaining within the scope of that which is claimed.

While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims. 

1. A rotor assembly for a supercharger comprising: a first rotor section; and wherein said first rotor section is formed from powdered metal.
 2. The rotor of claim 1, further comprising: at least one other rotor section affixed to said first rotor section; and wherein said at least one other rotor section are formed from powdered metal and is substantially similar in shape to that of said first rotor section
 3. The rotor of claim 2, wherein each of said first rotor section and said at least one other rotor section have a plurality of lobes and wherein said plurality of lobes are substantially hollow.
 4. The rotor of claim 2, wherein each of said first rotor section and said at least one other rotor section has at least one axially extending locating feature and at least one recess sufficiently configured to receive said at least one axially extending feature and wherein said at least one recess of said first rotor section cooperates with said at least one axially extending locating feature of said at least one other rotor section to locate said first rotor section with respect to said at least one other rotor section.
 5. The rotor of claim 2, wherein each of said first rotor section and said at least one other rotor section are affixed through one of brazing, copper infiltration, and welding.
 6. The rotor of claim 2, wherein each of said first rotor section and said at least one other rotor section have a plurality of lobes and wherein said plurality of lobes are straight in shape.
 7. The rotor of claim 2, wherein each of said first rotor section and said at least one other rotor section have a plurality of lobes and wherein said plurality of lobes are helical in shape.
 8. The rotor of claim 2, further comprising a shaft and wherein said first rotor section and said at least one other rotor section are mounted on said shaft.
 9. The rotor of claim 2, wherein each of said first rotor section and said at least one other rotor section are formed from one of steel, aluminum, and aluminum alloys.
 10. A supercharger assembly comprising: a housing defining an inlet passage operable to induct intake air into the supercharger assembly, an outlet passage operable to exhaust said intake air from the supercharger assembly, and a rotor cavity; a first rotor assembly rotatably disposed within said rotor cavity; a second rotor assembly rotatably disposed within said rotor cavity and interleaved with said first rotor assembly; wherein each of said first and second rotor assemblies include: a first rotor section; at least one other rotor section affixed to said first rotor section; and wherein said first rotor section and said at least one other rotor section are formed from powdered metal and are substantially similar in shape; and wherein said first and second rotor assemblies cooperate to communicate said intake air from said inlet passage to said outlet passage.
 11. The supercharger assembly of claim 10, wherein each of said first rotor section and said at least one other rotor section have a plurality of lobes and wherein said plurality of lobes are substantially hollow.
 12. The supercharger assembly of claim 10, wherein each of said first rotor section and said at least one other rotor section has at least one axially extending locating feature and at least one recess sufficiently configured to receive said at least one axially extending feature and wherein said at least one recess of said first rotor section cooperates with said at least one axially extending locating feature of said at least one other rotor section to locate said first rotor section with respect to said at least one other rotor section.
 13. The supercharger assembly of claim 10, wherein each of said first rotor section and said at least one other rotor section are affixed through one of brazing, copper infiltration, and welding.
 14. The supercharger assembly of claim 10, wherein each of said first rotor section and said at least one other rotor section have a plurality of lobes and wherein said plurality of lobes are one of straight and helical in shape.
 15. A method of forming a rotor assembly for a supercharger assembly, the method comprising: forming a first rotor section and at least one other rotor section from powdered metal; and affixing said at least one other rotor section with respect to said first rotor section to form the rotor assembly.
 16. The method of claim 15, wherein each of said first rotor section and said at least one other rotor section have a plurality of lobes and wherein said plurality of lobes are substantially hollow.
 17. The method of claim 15, wherein said affixing said at least one other rotor section with respect to said first rotor section to form the rotor assembly is performed by one of brazing, copper infiltration, and welding.
 18. The method of claim 15, further comprising mounting said first rotor section and said at least one other rotor section on a shaft.
 19. The method of claim 15, further comprising indexing said at least one other rotor section with respect to said first rotor section prior to affixing said at least one other rotor section with respect to said first rotor section.
 20. The method of claim 19, wherein each of said first rotor section and said at least one other rotor section has at least one axially extending locating feature and at least one recess sufficiently configured to receive said at least one axially extending feature and wherein said at least one recess of said first rotor section cooperates with said at least one axially extending locating feature of said at least one other rotor section to aid in indexing said at least one other rotor section with respect to said first rotor section. 